Apparatus and method for positionally enhancing an image

ABSTRACT

The present disclosure teaches a method and apparatus for use in stabilizing images. The invention operates to sense the position of the image to be stabilized, compare the position of the image to a reference to determine a displacement value responsive thereto and change a correction element located in the conveyance path of the image in response to the displacement value to cause a compensating displacement of the image.

This application is a division of application Ser. No. 08/775,478 filedDec. 30, 1996, now U.S. Pat. No. 5,793,053 which is a division ofapplication Ser. No. 08/730,768 filed Oct. 16, 1996 now U.S. Pat. No.5,635,725 which is a continuation of application Ser. No. 08/195,422filed Feb. 15, 1994 (abandoned).

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to the field of spatially stabilizingelectromagnetic radiation images which are the result of radiationincident on a reflective or transmissive surface. The invention findsparticular use for stabilizing projected optical images from projectorssuch as film and television projectors, graphics printers or imagesphotographed by a camera such as a still video or television camera.

In the presentation, viewing or capture of images, problems often occurdue to mechanical imperfections such as vibrations, distortions,tolerance buildup, wear, chemical stability, electrical noise and a hostof other forms of mechanical, optical, chemical and electrical problems.These problems can cause movement, jitter and/or distortion of theimage, whether the image is being presented for viewing by biologicaleyes, analysis by machines, viewed for enertainment or captured forstorage. Elecotro mechanical and optical mechanical devices such asprojectors and cameras are highly susceptible to such problems. Theseproblem are present no matter what type of electromagnetic radiation isbeing utilized, be it optical, microwave, X-ray, cosmic rays etc. Anyelectromagnetic image or image instrument which is subject to mechanicalvibration in the utilization thereof may be improved by the presentinvention.

One of the most common of mechanical effects occurs with film projectorsand is called gate weave in the motion picture industry. Gate weaveresults in a moving and jittery image being presented on the motionpicture screen when the movie is projected due to slight movement of theprojected film image. The main cause of gate weave in this instance isthe improper positioning of the film image in the film gate or apertureof the projector from one frame to the next. The improper positioning ofthe image is a result of the above mentioned problems, either in theprojector, the camera shooting the film or the intermediate filmprocessing, but most commonly is due to the wear and tear of thesprocket holes in the projected film occuring over prolonged use. Thesprocket holes are used by the projector intermittent gear to positionthe film in the projector aperture for the momentary presentation ofeach frame, with the edges of the holes requiring critical alignmentwith respect to the film image. As the film is projected over and over,these edges tend to wear unevenly.

In addition, for very old films, chemical changes in the film emulsionand/or base cause physical distortion of the film image with respect tothe sproket holes and film edges. These problems also result in gateweave.

While it is possible to minimize the various effects mentioned above,the problem of wear of the sprocket holes as well as chemical distortionof the film emulsion or base over time remain as serious problems whichare not generally correctable after the damage occurs. It is desirablethen to reduce the visibility of such movement, jitter and/or distortionduring the projection of the film in order to present a more stableimage for the aforementioned viewing. In addition when the image isbeing viewed by a machine, such as by a television camera, it is oftennecessary to stabilize the image on the image sensing element.

In addition to film gate weave, there are many types of imagepresentations where image movement and jitter are problematic, eitherdue to the image system itself, or due to the system being required todisplay or view images which have had movement or jitter "recorded in".Generally, anytime it is desired to mechanically focus or align an imagejitter and movement can be a problem. Such recording in often happenswhen the image was generated or transferred from one storage medium toanother, and results in the jitter being recorded into the image. Beyondsuch recording in, no amount of mechanical stability correction of theimage media can correct the jitter. What is needed is correctivecanceling mechanical jitter of the image media itself, the imagerecovered therefrom or the projected or viewed image to effectstability. This corrective canceling action would be required even ifthe subsequent projection or viewing of the image were made without anyjitter or other mechanical problems at all. For example, if a video taperecording were made of a jittering film, the present invention couldpreferably be used to correct the film jitter during the recording, orif such were inconvenient or impossible, the invention could be used tocurrect the subsequent use of the video tape recording.

Examples of such systems which might be required to display a moving,jittery or distorted image include electro and optical mechanicalprinters, projectors and viewers as well as television and computerdisplays and printers, including more familiar electronic displays.

2. Description of the Prior Art

In the Prior art it is known to apply considerable mechanical precisionto the movement and holding of the image bearing or image receivingelement of imaging systems. In particular film projectors havingelaborately designed film movement and intermittent mechanics are wellknown. In the field of acquiring images, such as in film and televisioncameras, elaborate spring, and other types of vibration and movementdamping mechanisms are used, these including electromechanical gyroscopemechanisms to hold the camera or its mounting platform steady.

It is also known in the television industry to electronically correct ajittering television image by the electronic process of moving the videoimage signal with respect to its horizontal and vertical synchronizingpulses with the aid of complex motion detection circuits and framememory control. Such systems do not lend themselves to improvement ofexisting projection and camera equipment and in particular to theimprovement of existing motion picture film and television projectors.

OBJECTS OF THE INVENTION

It is an object of the invention to stabilize an image in a first formby sensing its position with respect to a reference and altering itsconveyance path in response thereto in order to improve the stability ofthe image in the first or another form.

It is another object of the invention to position an electromagneticradiation image by sensing the image in a first form and altering thepath of the electromagnetic radiation which creates the image in thefirst or a second form in order to improve the positional accuracy ofthe image.

It is a yet another object of the invention to stabilize an opticalimage by sensing its position and refracting the light which creates theimage in response thereto in order to improve the stability of theimage.

It is still another object of the invention to sense an optical image tobe stabilized, compare the position of the image from one moment in timeto another to determine a displacement value responsive to thedisplacement thereof in at least one dimension and changing an opticalcorrection element located in the light path of the image in response tothe displacement value to cause a compensating displacement of theimage.

It is a further object of the invention to sense the position of aseries of projected image frames to be stabilized before projection,compare the position of the image from one frame to the image fromanother frame to determine a displacement value responsive to thedisplacement thereof and changing an optical correction element locatedin the light path of the projected image in response to the displacementvalue to cause a compensating displacement of the projected image.

It is yet a further object of the invention to sense the position of anelectromagnetic radiation image which is to be recorded by a recordingelement in a series of frames, to stabilized that image before and/orduring recording, by comparing the position of the image from one timeto another to determine a displacement value responsive to thedisplacement thereof on the recording element, and changing aelectromagnetic radiation correction element located in the radiationpath of the recorded image in response to the displacement value tocause a compensating displacement of the recorded image on the recordingelement.

It is still a further object of the invention to allowing sensing of animage in a fashion which does not interfere with the projection or therecording of the image in order that the image may be stabilized beforeand/or during such projection or recording.

It is further another object of the invention to sense an image positionas conveyed in a first electromagnetic form and correct the imageposition as conveyed in a second electromagnetic form.

It is yet further another object of the invention to sense an imageposition at a first location and correct the image position in a secondlocation.

It is still further another object of the invention to sense an imageposition at a first time and correct the image position at a secondtime.

It is yet still further another object of the invention to correct animage position by tilting an optical flat in the radiation beam of thatimage.

Other objects and a fuller understanding of the invention may be had byreferring to the following description and claims, taken in conjunctionwith the accompanying drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a diagram of the preferred embodiment of the invention asused with a film projector.

FIG. 2 shows a diagram of the internal components of elements 9, 10 and11 of FIG. 1.

FIG. 3 shows diagram of the preferred embodiment of the invention asused with a television camera.

FIG. 4 shows a diagram of an embodiment of the sense CCD array element7.

FIG. 5 shows another embodiment of the sense CCD array element 7.

FIG. 6 shows a diagram of an embodiment of the invention as used withthe sense CCD array of FIG. 4 or 5.

FIG. 7 shows a side view of the the image projection path of a projectorincluding the invention.

FIG. 8 shows exaggerated side views of the preferred optical flat usedfor spatial correction of an image.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 shows a diagram of the preferred embodiment of the invention asused in motion picture film projection. The invention consists of priorart projection elements including the projection lamp 1, condenser lens2 moving film 3, film aperture plate 4, shutter 5 which may be modifiedaccording to the invention and projection lens 6. It should be notedthat often the condenser lens 2 is replaced by or augmented with aspherical or elliptical mirror behind the projection lamp 1. Thisdiagram may also represent an electronic projector by replacing the filmwith an LCD array as is commonly known. It will be realized by oneskilled in the art that this diagram could also represent an imageacquisition system if the light is coming in the lens and the film or aCCD array were being exposed as will be discussed later with respect toFIG. 3.

The invention includes the addition of an image sensor CCD array 7 withimage focusing mirror 8 operable to focus the film image on the sensor.It is shown in preferred form that the sensor be arranged to view thefilm frame within the aperture directly, however it may also be arrangedto view the projected image on the screen as is shown by ALT. 7 and ALT.8.

Further parts of the invention include correction optics 10 operable todeflect the light of the projected image which emanates from theprojection lens. The correction optics are preferred to include amovable lens element which element is driven by electronic voice coilactuators whereby the movement of the lens element is effected byvarying the current in the voice coil. It is preferred to use two axismovement, horizontal and vertical, with two sets of voice coilactuators. These actuators and their associated electronics are shown in10. Alternatively, the correction optics may be placed between theprojection lens and film as shown by Alt. 9, or may be incorporatedotherwise to move the projected image, for example by incorporation inthe projection lens 6 or by physically moving the film 3 in or with theaperture. It is preferred however that the correction optics be locateddirectly in front of the lens in order to minimize the cost of addingsuch to existing projectors. The control of the correction optics 9 isperformed via the optics support and movement 10 by the CCD andstabilizing electronics 11.

The motion of the film between frames is sensed, such as by a pulldownsensor 12 which optically senses the sprocket holes of the film. Whenthe film is moving, either a sprocket hole is moving past the sensor, orthere is no hole in front of the sensor. When the film is steady, asprocket hole remains stably in front of the sensor. Alternatively, thepulldown sensor may be coupled to the intermittent sprocket or to theGeneva movement, or the motion of the film may be detected by detectingthe actual movement of the image via the CCD array 7.

In operation, the shutter(s) 5 block the light from the projection lampand the film is moved to the next frame by the intermittent gear, as iswell known in the art. The movement of the film is sensed by one of thevarious methods taught above, and at the precise moment when the filmmovement is stopped at the new frame, the CCD sensor 7 is strobed totake an instant snap shot of the new image in its stable position. TheCCD and stabilizing electronics measures the position of the new frameimage relative to the previous frame image, and sends two correctionsignals, one horizontal and one vertical, to the optics support andmovement circuits 10 which cause the correction optics 9 to repositionthe image from the new frame to match the image position from theprevious frame. The Shutter(s) 5 then open to allow light to passthrough the film and onto the screen via the projection lens 6 andcorrection optics 9.

It is important that the image be positioned before the shutter opensfully. In a normal Geneva intermittent, the shutter is closed for some60° of the 360° intermittent cycle. At the conventional projection speedof 24 frames per second the shutter will be closed for about 7milliseconds. The film will be stable for only a fraction of amillisecond before the shutter starts to open. While it is notabsolutely necessary that the image be positioned before the shutterstarts to open, it is nevertheless desirable in order to prevent imageghosting which is caused by image movement after some light is letthrough the shutter. In order to allow the CCD array to view the filmimage before light is let through the shutter, an alternate filmilluminator 13 is used.

It is preferred that this illumination from 13 be invisible to the imageobserver, thus ultraviolet illumination and sensing is preferred. Theimage sense lens 8 is preferred to include a filter coating which passesonly ultraviolet light. This has the advantage of allowing the CCD arrayto have a relative constant illumination which is somewhat independentof the shutter operation. Keeping in mind that the projection lamp 1 maywell emit a considerable amount of ultraviolet light which will beshuttered onto the CCD array, it would be desirable to add anultraviolet block filter at the location of the condenser lens 2.

Alternatively, the ultraviolet energy from projection lamp 1 can be usedto illuminate the film frame for the CCD array and thus eliminate theneed for the separate sense illumination 13. Such operation may beaccomplished by one skilled in the art by replacing the shutter(s) 5with a material which passes ultraviolet light but blocks visible light.Other suitable illumination schemes may be had to achieve the desiredoperation of illuminating the new film frame just after intermittentmovement has stopped, without passing appreciable visible illuminationto the viewer, for example by combinations of visible and invisibleillumination, or by adding shuttering, for example by moving shutter 5between the film and projection lens, or in front of the projectionlens.

It should be noted here that near ultraviolet light is preferred to farultraviolet. Often the film stock is prepared by formulation or coatingto specifically reflect ultraviolet light in order to reduce damage tothe film and emulsion. Near ultraviolet will often penetratesufficiently for successful operation while far ultraviolet will fail.Alternatively, infrared may be utilized, however given the amount ofstray infrared caused by the heating of the aperture by the projectionlamp, such is not as desirable as ultraviolet.

Other wavelengths may be used as well, including visible wavelengths atlow intensity without additional shuttering or at high intensity withadditional shuttering. In particular, an additional shutter such as anLCD may be added to the correction optics to block the senseillumination during film movement and during image correction. Thisadditional shutter may even be caused to open lagging the first shutter5 opening by a small amount of time to give the correction optics timeto position. Such lag will of course cause a slight dimming of theprojected image and depending on the projection light intensity maycreate some heat dissipation problems.

Optical lenses, filters and other components to construct the abovepreferred embodiment of the invention are well known to those ofordinary skill in the art and are available from numerous sourcesincluding Edmund Scientific, 101 E. Gloucester Pike, Barrington, N.J.08007 and Oriel Corporation, 250 Long Beach Blvd. Stratford, Conn.06497.

FIG. 2 shows a detailed diagram of the CCD and stabilization electronics11 and the optics support and movement electronics 10 as they arecoupled to the correction optics 9. The video from the CCD array 7 iscoupled to analog processing circuitry shown as clamp and gain circuit14 where the sampled analog signal is conditioned for application to ananalog to digital convertor 15. A-D 15 outputs a digitized version ofthe CCD video which is coupled to a frame delay or memory 16, and anedge detector 19. If it is desired to use the CCD video to detect filmintermittent movement, the video from the A-D may also be coupled to theFrame Projection Detector 21 with, or in place of the signal frompulldown sensor 12. The frame delayed video from 16 is also coupled toan edge detector 17.

Edge detectors 17 and 19 compute horizontal and vertical edges andcouple these edges to a motion detector 20 where the motion between areference, which in the preferred embodiment is the previous displayedimage stored in the frame delay 16, and the current frame from 19 arecompared to determine the degree of movement. The edge detectors 17 and18 may be eliminated if the sensor CCD array is made to be edgesensitive by its construction. Motion detector 20 operates to subtractthe previous amount of correction from the H and V edges from 17, andthen correlate these corrected edges with the H and V edges from 19 inthe horizontal and vertical directions to compute horizontal andvertical movement. It would also be possible to store only the H and Vedges from 19 in the Frame delay 16, thus eliminating the redundant edgedetector 17. This will require some additional manipulation of thememory since two signals will be stored rather than one.

The reference may also be derived by spatially or temporally integratingor filtering the images in a recursive or other type filter in order toarrive at an estimated central image representing the optimal positionof the image. Such a reference has the advantage of reducing erroraccumulation in the motion detector, since any positional errors areintegrated or filtered out of the system by utilization of a referencewhich represents a sort of spatially average of the jittering images.Such a recursive filter may be simply implemented by storing into thememory a small percentage of the new video and a large percentage of theoutput of the memory. 1/32 and 31/32 are the preferred percentages,however others may be used providing their sum is precisely equal toone. Such recursive filters are well known in the art.

Once the Motion Detector 20 has computed the proper amount of motion ofthe present frame with respect to the displayed position of the previousframe, the H and V motion amounts are coupled to the Optics Support andMovement circuit 10.

The Optics Support and Movement circuit 10 receives the H and V motionsignals and provides a corresponding amount of actuator drive signal tothe H and V actuators 24, 25, 26 and 27 to cause the movable element ofthe Correction Optics 9 to move and thus reposition the image to theproper location. The Optics Support and Movement circuit 10 alsoincludes H and V position sensors 29 and 30 which sense the position ofthe movable element in order to verify its proper position. In thediagram shown, the Correction Optics 9 consists simply of a transmissiveflat element which for light is known as an optical flat. Thetransmissive flat element is preferred to have a diameter which willallow the full beam of light from the projection lens 6 to pass throughwith minimum attenuation and a thickness approximately 20% of thediameter, and is prefered to be coated for maximum light transmission.The diameter is preferred to be 1.5 times the diameter of the 1/2intensity diameter of the light beam. Correction is simply achieved byvarying the tilt of the flat which causes diversion of the light beamdue to refraction in the denser optical flat.

Element 9 is mounted on springs or a gimbel (not shown) behind theactuators 24-27 (in the direction perpendicular to the drawing) in orderthat the magnets on element 9 may be attracted or repulsed by theelectromagnetic field created by the actuator. The attraction andreplusion will cause the optical flat 9 to tilt about its center, up ordown, left or right. By tilting the optical flat 9, the projected beamis correspondingly caused to be displaced up or down, left or right.

FIG. 7 shows a side view of the lamp 1, image plane 47, projection lens6, actuators 25, 26 and 27, and the optical flat with attached magnets9.

FIG. 8 shows exaggerated side views of the optical flat 9 tilted up anddown demonstrating how the light beam is moved by the tilting of 9.While the range of correction is limited with this type of correctionoptics, it performs well and is inexpensive to construct. It can beplaced close to the front of the projection lens where there is usuallyroom on existing projectors, and it is out of focus, thus dust andimperfections will not adversely affect the projected image. It alsodoes not adversely affect the focus of the projected image, and allowsoperation with various lenses such as standard and anamorphic lenses.Alternatively, Correction Optics 9 can be placed anywhere in theprojected beam, in front, behind or inside the projection lens.

If it is desired to increase the correction range of the correctionoptics element 9, one of ordinary skill in the art will be able toresort to various alternate designs using other optical components likemirrors, wedges and/or lenses to achieve the increased range, as will beknown from the teachings herein. The methods of actuating 9 may bechanged as well, for example by driving with solenoids, piezoelectricactuator cells, linear stepper motors or other well known actuatingmechanisms.

In the preferred embodiment, there is little or no rotation of theimage, and thus rotation correction is not provided. It is quitepossible however to provide a third rotation correction circuits andactuators should such correction be desired. The Motion Detector 20 willdevelop a rotation error from the H and V edges and couple that error toa rotation actuator through a rotation driver. A rotation sensor wouldalso be desired. An optical device known as a dove prism is capable ofperforming optical rotation. The image is projected through thelongitudinal axis of the prism. To rotate the image, the prism ismechanically rotated about the longitudinal axis which causes imagerotation through an angle twice as much as prism rotation. Such prismsand the mechanical positioning devices to controllable rotate them areavailable from numerous optical suppliers, including the aforementionedEdmond Scientific and Oriel Corporation.

FIG. 3 shows how the invention may be used in a camera system.Illumination is provided through the lens 6 and on to a film or othersensor 31. Light from the image may be passed through a beam splitter 32in order that light to which the sense CCD array 7 is sensitive iscoupled thereto. The light falling on the array 7 is thus used to adjustthe correction optics 9 via circuits 10 and 11 as in FIG. 1.Alternatively, the sense CCD array 7 may be optically coupled to viewthe surface of the film or sensor 31, if that surface reflects enoughlight to which the sense CCD array is sensitive. The beam splitter 32could also be used with the projector of FIG. 1. There is no requirementthat this camera be a motion camera, as the system will operate as wellwith still imaging.

When film is used for 31, an LCD, rotating mechanical or other shutteris provided in the correction optics 9 or elsewhere in the optical path.The shutter operates to pass only light the film is not sensitive to orotherwise prevent exposure, except when the film is being exposed whenit passes light the film is sensitive to. LCD shutters or light valvesare well known in the art and are available from a number of suppliersincluding Meadowlark Optics, 7460 Weld County Road 1, Longmont, Colo.80504. Mechanical shutters are also well known, such as the prior artrotating shutter 5 of FIG. 1.

In the case of a television or other electronic camera, 31 may be anelectronic sensor such as a CCD array as is well known in the art. Theshutter in 9 may be eliminated if the sensor can be turned on and off.The electronic sensor is caused to turn on and off in order that theimage position may be adjusted while the sensor is off, with the sensorturned on for exposure after the image is properly positioned by 9.

With all of these systems, light is coupled from the image to the senseCCD array 7, but exposure of 31 is blocked. The sense CCD operates with9, 10 and 11 to adjust the position of the image. When the image isproperly adjusted, the exposure of 31 is commenced. It is possible tomaintain the adjustment of the image during the exposure simply bymaintaining the operation of the system therewith. As with the alternatelocation of 7 and 8 in FIG. 1, the camera may also arrange 7 to view theimage directly through a separate lens. It would also be possible toeliminate the sense CCD array 7 and use the Main CCD Array for bothsense and recording functions by simply coupling the output signal to11.

FIG. 4 shows a suitable arrangement for the Sense CCD Array 7 which iscomprised of two linear CCD arrays 33 and 34 which are preferred tocomprise 512 elements each. The Fairchild CCD153 element will work wellfor this element and is available from Loral Fairchild, Imaging Sensors,Milpitas, Calif. 95035. Other sensors which would be suitable for thisfunction are available from. Dalsa, Inc. 605 McMurray Road, Waterloo,Ontario, Canada N2V 2E9. The two arrays are mounted perpendicular to oneanother with one directly behind the other, with the image beingoptically coupled to be focused on the sensors. The back array has themiddle few elements blocked by the front element, however this resultsin only a slight loss of performance as these blocked elements may bemasked in the correlation IC. Light from the image is focused on thesesensors in order that the output will represent an intensity function ofthe image in one vertical line and one horizontal line. By the use ofsingle line CCD sensors, the need for the edge detectors 17 and 19 iseliminated.

FIG. 5 shows an alternate arrangement for the Sense CCD Array 7 which iscomprised of two linear CCD arrays 38 and 39 which are also preferred tocomprise 512 elements each. As is shown in this figure, the sensors canbe arranged separately, with each one having an optical coupling of theimage. The two arrays are mounted perpendicular to one another onopposite sides of a beam splitter which is utilized to split the lightfrom image 35 which is focused by lens 36 on the two. In this fashion,all of the CCD elements are illuminated, but at the expense of anoverall light reduction for each one. Alternatively, two lenses may beused one to independently optically couple each sensor to the image.

FIG. 6 shows the signal processing for the stabilization electronics of11 when used with the Sense CCD Array 7 as configured in FIG. 4 or FIG.5. Each array is coupled to a Clamp 29 Gain and Processing circuit 40which processes the sampled analog video signal from the array andcouples it to the A-D 41. Such arrays, clamp gain processing circuitsand A-D convertors are well known in the art as single line CCD array,digital output cameras. It is possible to purchase a single line CCDarray camera having all of these components integrated from variousmanufacturers. In particular a camera using the suggested CCD153element, the DDC1200R camera is available from the aforementioned LoralFairchild. This camera achieves a 26 μs minimum exposure time and a 20MHz pixels per second maximum video output rate. Two such cameras areused, one focused horizontally on the image and one focused verticallyon the image. Dalsa, Inc. also supplies line array cameras. An externalA-D convertor is needed with the DDC1200R with a preferred conversionaccuracy of 8 bits. The construction of a proper convertor is wellwithin the ability of one of ordinary skill in the art. The BrooktreeBt252 8 bit image digitizer is suitable for this A-D convertor. Thispart and application notes on the theory, construction and properoperation of this A-D convertor is available from Brooktree as well.

The 8 bit digital video from 41 is coupled to a correlator 43 of 512bits in length and a delay 42 which is preferred to be 512 bits long.The delayed signal is first clocked into the correlator 43 and held.Next the new 512 bits are clocked into the correlator and past the old512 bits as they arrive from the A-D. The new 512 bits aresimultaneously clocked into the delay 42 for storage until needed at thenext frame. Correlators are well known in the art and the TRW TMC2023will be found to be a suitable component for constructing this portionof the invention. This part is available from Raytheon (formerly TRW LSIProducts) La Jolla, Calif. 92038. Applications notes on the theory,proper construction and operation of multi bit correlators are alsoavailable from Raytheon.

As the new 512 bits are clocked through the correlator and past the old512 bits a correlation or measure of the matching of all of the samplesis performed. If for example an old bit has the value of 0 and a new bita value of 225, the correlation is 256-(225-0) or 31, not a high match.If the two bits have the same value Y, the correlation of those two bitsis 256-(Y-Y) or 256, a perfect match. The correlator operates to sum allof the individual matches over the 256 samples which are being compared.These sums will vary clock by clock from 0 to (512×256). For unmatchedsignals the correlation will hover around mid range, and for matchedsignals the correlation value will be very high, exhibiting a pronouncedpeak as the new signal is shifted through the correlator and comes intoalignment with the old.

The peak position circuit counts the number of clock cycles since thestart of the frame, and stores the count of the clock cycle at which thehighest correlation number occurs. For example, if the peak occurs at512 clocks, the two signals are matched and thus the two images arecoincident. If the peak occurs at 514 clocks, the new image is displacedtwo CCD elements to the right of the old (assuming the first element ison the right of the image).

The action of measuring the location of the peak is performed simply bystoring the count and correlation value each time the new correlationvalue is larger than the stored correlation value. After 1024 clocks,the peak position circuit will have stored the count where the highestpeak occurred, which count corresponds to the number of clock cycleswhere the new and old video signals matched. The difference betweenthese counts (normalized to 512 counts or no error) is the number ofclock cycles of the displacement between the new and the old frame inunits of CCD element spacing. The difference of new and old counts isoutput from 44 as the frame to frame motion value.

The previous frame to frame motion value stored in 45 is subtracted by46 from the current frame to frame motion value from 44 to arrive at themotion of the current frame with respect to the position (on the screen)of the displayed image. The motion value is then coupled to the OpticsSupport and Movement circuit 10 where it is used to reposition theCorrection Optics 9.

At scene changes, or where there are no edges to correlate, there willbe no clear correlation peak. In this event, the Peak Position circuit44 will sense that the correlation number is below a threshold. Thethreshold is preferred to be 98304 (384×2⁸), that is the number ofmatches for a correlation peak must be greater than 384×2⁸. If the peakis below the threshold, the Peak Position circuit 44 outputs a zeroframe motion value and clears the store 45 to zero, which will cause azero motion value to be passed to 22 (or 23).

As will become apparent to one or ordinary skill in the art from thepresent teachings, the invention may also be utilized as resolutionenhancing system. Images may be recorded in high resolution withsubsequent display of each high resolution image by a plurality offrames of lower resolution images. The image correction optics 9 isutilized to position the pixels of the lower resolution images to theproper position on the displayed image. For example, an image isrecorded with 200 pixels across the image width. A first frame isdisplayed utilizing all of the odd pixels, 1, 3, 5, etc. followed by asecond frame display of all of the even pixels 2, 4, 6, etc. During thedisplay of the second frame the correction optics causes the image toshift by a pixel width, causing pixel 2 to be displayed between pixels 1and 3, 4 between 3 and 5, etc. This operation is simply achieved byadding a small offset to the Motion signal from 20. This operation maybe performed in either presentation or capture of images.

The description of the preferred embodiment of the invention, as well asseveral alternate embodiments are made herein by way of example withresort to some generality as to the specific details of individualelements which are well known to those of ordinary skill in the art.Thus from the teachings herein, one of ordinary skill in the art will beable to practice the invention and in particular to successfullyconstruct and practice the preferred embodiment without resulting tofurther invention or excessive experimentation.

While the preferred embodiment of the invention described herein findsconsiderable use in the film projection field, it will be recognized bythose skilled in the art to which various image devices are found thatfrom the teachings herein the invention may be adapted to be utilizedwith such other devices.

It will be appreciated by those of ordinary skill in the art that theterms given herein which are particular to a given art, such as the filmprojection field, are meant by the inventor to also encompass thesimilar or kindred terms of other fields. For example the term projectoris meant to apply to all, projection, viewing and display deviceswhether for film, television, computer, printer or other fields. Theterm gate weave is meant to apply to any image motion, jitter and/ordistortion, whether by the image itself or the projecting or viewingapparatus. The term viewing is intended to include viewing, analysis,acquisition, inspection or other use of an image by eyes or machines.The terms optical and optics are intended to pertain to all particle orelectromagnetic radiation pertaining to images, rather than to just thecommon meaning associated with visible light. The term image is meant toinclude all the various forms of the image, for example the image on thefilm, the image as projected on the Sense CCD array, the image asprojected on the projection screen, the image being recorded, the imagestored as electronic information and the image on the recording sensor.Image, depending on the context, may refer to a virtual image, an imageon a recording medium such as electrons with a memory, film or tape,emulsion, ink, chemicals or other particles on a base such as film orpaper. The word image is to be interpreted with breadth unlessspecifically defined as pertaining to a particular form. It will also beunderstood that while the words element, device and circuit maysometimes carry with them some implication of optical, mechanical, orelectrical embodiments, it is well known in the art that they havebroader meanings. For example, an element is not just an element of anoptical lens, but may also be a mechanical, electrical or fluid element.As used herein, location is intended to refer to a particular positionin space. Image is used herein as commonly used in the art as a spatialdistribution of a physical property, such as radiation, electric charge,conductivity or reflectivity, mapped from another distribution of eitherthe same or another physical property. This definition fits for examplethe view of a light emitting or light reflecting object, or a radiationimage as focused or projected on a plane in space in a virtual or realsense. It may be noted that a beam of light which caries an image doesnot fit this definition unless it is focused to the extent where ittakes on a spatial distribution which is mapped from anotherdistribution.

Although the description of the preferred embodiment of the invention ismade herein with a certain degree of particularity, it is understoodthat the present disclosure of the preferred form has been made only byway of example and that numerous changes in the details of constructionand the combination and arrangement of parts may be resorted to withoutdeparting from the spirit and the scope of the invention as hereinafterclaimed.

What is claimed is:
 1. The method of correcting gate weave in aprojector wherein each image of a series of frame or field images isinitially situated near a known location with each said image of saidseries being exposed onto a surface via image light which travels fromsaid image to said surface via a light path, with said gate weaveoccurring due to said frame or field images being so situated relativelyimprecisely at said known location, said method including:a) during atime interval after said initial situating of said image, sensing atleast a portion of said image with an electro optical sensor to providea sensed portion signal, b) digitizing said sensed portion signal toprovide a current portion signal in response thereto, c) inspecting saidcurrent portion signal to determine the displacement of said image froma desired position, d) altering said light path in response to saiddisplacement to cause a compensating displacement of said image light.2. The method of claim 1 wherein said displacement in step c) isdetermined in response to at least one previously provided currentportion signal of step b) which has been stored in a digital memory. 3.The method of claim 1 wherein said method is used with a film projectorhaving a shutter with light projecting through a film frame located inan aperture to provide said image light, said method further includingcompleting steps a) thru d) before said shutter is opened to allow saidimage light to pass through said film frame portion.
 4. The method ofclaim 1 further including shuttering said light path of step d) untilthe completion of said altering step d) with a shutter located betweensaid known location and said surface.
 5. The method of claim 1 furtherincluding illuminating said portion of said image during step a) withlight which is not visible to a human viewer.
 6. The method of claim 1further including illuminating said portion of said image withultraviolet light during step a).
 7. The method of claim 1 furtherincluding correlating said current portion signal with a referencesignal representing said desired position as part of step c).
 8. Themethod of claim 1 further including correlating said current portionsignal with a reference signal representing said desired position inhorizontal and vertical dimensions as part of step c) andcorrespondingly optically altering said light path in horizontal andvertical dimensions as part of step d).
 9. The method of claim 1 usedwith a film projector having an intermittent film movement and a shutterwith light projecting through a film frame located in an aperture, saidmethod further including detecting the position of sprocket holes insaid film in order to determine the time interval which occursimmediately after said film has ceased movement due to pulldown actionas part of step a).
 10. The method of claim 1 used with a film projectorhaving an intermittent film pulldown action provided by an intermittentmechanism and a shutter with light projecting through a film framelocated in an aperture, said method further including detecting theposition of the mechanics of said intermittent mechanism which advancesthe film in order to determine the interval immediately after the filmhas ceased movement due to said pulldown action as part of step a). 11.The method of claim 1 used with a film projection system furtherincluding detecting the light intensity of rear illumination of the filmframe in order to determine the interval immediately after said filmframe has ceased movement due to pulldown action as part of step a). 12.The method of claim 1 further including as part of step d), mechanicallypositioning an optically refracting element placed in said light path inresponse to said displacement thereby causing said compensatingdisplacement.
 13. The method of claim 1 further including as part ofstep c), detecting edges of said image as conveyed by said currentportion signal, and comparing said edges with edges of a known referencesignal.
 14. The method of maintaining proper rotation of a projectedimage formed by projection of light from an image medium via a lightpath onto a surface including the steps of:a) sensing at least a portionof said image medium with a sensor to provide a sensed portion signal,b) digitizing said sensed portion signal to provide a current portionsignal in response thereto, c) detecting the rotation of said image assaid rotation thereof is conveyed by said current portion signal withrespect to a rotation reference signal representing the desired positionof said image to determine the rotary displacement of said imagerelative to said desired position, and the further step of, d) opticallyaltering said light path in response to said rotary displacement tocause a compensating rotary displacement of said projected light.
 15. Ina film projection method having a number of steps including at least:individual film frames being positioned one at a time with respect to anaperture, shining or projecting light from a light source through thefilm frame so positioned with at least a portion of said light fallingonto at least a first surface, with optical element steps being includedat various positions in the path of said light to thereby project theimage carried by said film frame onto said first surface; the method ofimproving the positional stability of said image which is projected ontosaid first surface, said method including the further steps of:a)determining the position of said film frame relative to a desiredposition in relation to said aperture; b) in response to step a),deflecting the path of said light which has passed through said filmframe in order to cause a compensating movement of said image which isprojected onto said first surface.
 16. In a film projection methodhaving a number of steps including at least: individual film framesbeing positioned one at a time with respect to an aperture, shining orprojecting light from a light source through the film frame sopositioned with at least a portion of said light falling onto at least afirst surface, with optical element steps being included at variouspositions in the light path to thereby project the image carried by saidfilm frame onto said first surface; the method of improving thepositional stability of said image which is projected onto said firstsurface, said method including the further steps of:a) determining theamount of deflection of the path of said light which has passed throughsaid film frame which is necessary to position said projected image at adesired position on said first surface; b) deflecting the path of saidlight which has passed through said film frame in order to cause said acompensating movement of image which is projected onto said firstsurface.
 17. The method as claimed in claim 15 or 16 wherein said filmis positioned by an intermittent action step involving a first timeperiod of moving said film from one frame to the next followed by asecond time period where said film frame is held stably positionedrelative to said aperture thereby facilitating said projection of saidimage, with step a) of said method operating during said second timeperiod and being inhibited during said first time period.
 18. The methodas claimed in claim 15 or 16 wherein said film is positioned by anintermittent action step involving a first time period of moving saidfilm from one frame to the next during which time the projection of saidlight onto said first surface is inhibited, followed by a second timeperiod where said film frame is held stably positioned relative to saidaperture thereby facilitating said projection of said image onto saidfirst surface, with step a) of said method further including operationduring said second time period and being inhibited during said firsttime period.
 19. The method as claimed in claim 15 or 16 wherein saidfilm is positioned by an intermittent action step involving a first timeperiod of moving said film from one frame to the next during which timethe exposure of said light at said first surface is inhibited, followedby a second time period where said film frame is held stably positionedrelative to said aperture thereby facilitating said exposure of saidimage at said first surface, with step a) of said method furtherincluding operation during a first portion of said second time periodwhen projection of said light onto said first surface is inhibited. 20.The method as claimed in claim 15 or 16 wherein said film is positionedby an intermittent action step involving a first time period of movingsaid film from one frame to the next during which time the projection ofsaid light onto said first surface is inhibited, followed by a secondtime period where said film frame is held stably positioned relative tosaid aperture thereby facilitating said projection of said image, withstep b) of said method further including operation during a firstportion of said second time period when projection of said light ontosaid first surface is inhibited to pre-position an optical element so asto provide said deflection when said projection of said image on saidfirst surface occurs.
 21. In an image system where a series of imagesare projected by light from an image source location in a fashion whichintermittently exposes each image of the series at a first surface, themethod of deflecting the light conveying each said image projected fromsaid image source location onto said first surface to reducing unwantedmovement of said series of images at said first surface, said methodincluding the steps of:positioning a substantially flat optical elementin the path of said light between said image source location and saidfirst surface such that the path said light takes will be moved bymoving said optical element, moving said optical element in response tothe position of said image at said image source location, said movingtaking place while exposure of said image at said first surface isinhibited and holding the position of said optical element stable duringexposure of said image at said first surface.
 22. The method of aligninga projected image carried via a film frame located in a film gate whichimage is projected from said film frame onto at least a first surface,said method including the steps of:a) detect horizontal or verticalmovement of said film frame from the ideal position relative to the filmgate to provide horizontal positioning data and vertical positioningdata responsive to horizontal and vertical movement errors relative tosaid ideal position; b) process said horizontal positioning data andvertical positioning data to compensate for errors therein other thantrue horizontal or vertical movement errors of said film frame; c)modulate the light path of said projected image in response to saidprocessed horizontal positioning data and vertical positioning data ofstep b) to compensate for said horizontal and vertical positioningerrors.
 23. The method of claim 22 wherein step c) includes moving atransmissive flat element which is disposed at substantially rightangles to said light path which is projected from said film frame tosaid first surface in a fashion that said path travels through said flatelement and wherein said step of modulating said light path includestilting said flat element relative to said light path in response to atleast one of said processed horizontal positioning data or verticalpositioning data.
 24. The method of positioning an image on a firstsurface which image is projected via a light path from a film onto saidfirst surface, said method including the steps of:a) moving a frame ofsaid film into a location relative to an aperture; b) holding said filmsteady in said location for a time period; c) sensing the location ofsaid film at or after the time of the start of step b); d) in responseto step c), altering the position of said image on said first surface bymoving at least one optical element located in said light path and; e)after step d), holding the position of said element during the remainderof said time period of step b).